[ESS] calling a local installation of R from emacs

[Sashi Challa]

Hi,

I have emacs-ess installed on my unix machine.When ever I call R from emacs I get  particular version of R.
Recently I had to test some packages so I installed R locally in a directory. Now I want to be able to call this particular R version from emacs.
What exactly should I editing or adding for this purpose. I want to be able to call both my default and local installation of R.

Thanks for all your help

Regards
Sashi